High performance cable termination

ABSTRACT

A cable assembly comprising a connector with a termination that enables high density and high signal integrity. Shields of cables are terminated to a paddle card via a conductive structure attached to a surface of the paddle card. The signal conductors of the cables are terminated to pads on the paddle card that are exposed within openings of the conductive structure. Such a structure creates a ground structure per cable that provides low insertion loss and low crosstalk, even when multiple cables are aligned side by side and terminated in one or more rows. The cables may be drainless, enabling a large number of cables, such as eight cables, to be packed within the width of a paddle card specified in high density standards such as QSFP-DD or OSFP. The cables may nonetheless have large diameter signal conductors, enabling 2.5 or 3 meter assemblies with less than 17 dB insertion loss.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application is a Continuation of U.S. application Ser. No.16/716,176, filed Dec. 16, 2019, entitled “HIGH PERFORMANCE CABLETERMINATION”, which claims priority to and the benefit under 35 U.S.C. §119(e) of U.S. Application Ser. No. 62/780,504, filed Dec. 17, 2018,entitled “HIGH PERFORMANCE CABLE TERMINATION”. The entire contents ofthese applications are incorporated herein by reference in theirentirety.

BACKGROUND

The techniques described herein relate generally to electrical cableassemblies used to transmit signals between electronic devices, such asservers, routers and switches.

Cables are often terminated at their ends with electrical connectorsthat mate with corresponding connectors on the electronic devices,enabling quick interconnection of the electronic devices.

A cable provides signal paths with high signal integrity, particularlyfor high frequency signals, such as those under 28 Gbps using anon-return-to-zero (NRZ) protocol, above 50 Gbps using a pulse amplitudemodulation (PAM) protocol, and/or the like. Each cable has one or moresignal conductors, which is surrounded by a dielectric material, whichin turn is surrounded by a conductive layer. A protective jacket, oftenmade of plastic, may surround these components. Additionally the jacketor other portions of the cable may include fibers or other structuresfor mechanical support.

The components of the cable that predominately impact signalpropagation, i.e., the signal conductor, the dielectric and conductivelayer, are generally uniform over the length of the cable.Non-uniformities on a signal path, such as might be created by changesin shape or material of the components, give rise to changes inimpedance or promote mode conversion, which reduce signal integrity, asthese effects are manifested as insertion loss, crosstalk or otherundesirable effects.

The signal conductor, dielectric and conductive layer are flexible,giving rise to a desirable property of cables. The flexibility enablesuniform cable properties to be maintained even if the cable is routedwith many bends, promoting signal transmission with high integrity.

One type of cable, referred to as a “twinax cable,” is constructed tosupport transmission of a differential signal and has a balanced pair ofsignal wires, embedded in dielectric material, and encircled by aconductive layer. In addition to uniform dimensions of the signal wiresover the length of the cable, the spacing of the wires relative to eachother and to the conductive layer is maintained over the length of thecable because those components are positioned by the dielectric. Such acable may be formed by extruding the dielectric material around thesignal wires.

The conductive layer is usually formed using foil, such as aluminizedMylar, or wire braid wrapped around the surface of the dielectric. Theconductive layer influences the characteristic impedance in the cableand provides shielding that reduces crosstalk between signal conductorsin twinax cables that may be routed together as a cable bundle. Theconductive layer also forms the cable ground reference.

A twinax cable can also have a drain wire. Unlike a signal wire, whichis generally coated with a dielectric to prevent electrical contact withother conductors in the cable, the drain wire may be uncoated so that itcontacts the conductive layer at multiple points over the length of thecable. At an end of the cable, where the cable is to be terminated to aconnector or other terminating structure, the protective jacket,dielectric and the foil may be removed, leaving portions of the signalwires and the drain wire exposed at the end of the cable. These wiresmay be attached to a terminating structure, such as a paddle card of aconnector. The signal wires may be attached to conductive elementsserving as mating contacts in the connector. The drain wire may beattached to a ground conductor in the terminating structure. In thisway, any ground return path may be continued from the cable to theterminating structure.

SUMMARY

According to one aspect of the present application, a paddle card isprovided. The paddle card may comprise a surface comprising a pluralityof pads on the surface. The paddle card may comprise at least oneconductive structure electrically and physically connected to pads ofthe plurality of pads, wherein the at least one conductive structurecomprises a plurality of tabs, each tab extending upward from thesurface, and each tab of the plurality of tabs is configured forelectrical contact with an exposed shield of an associated cable.

According to another aspect of the present application, a cable assemblyis provided. The cable assembly may comprise a paddle card comprising asurface, wherein the paddle card comprises a first plurality of pads anda second plurality of pads on the surface. The cable assembly maycomprise a plurality of cables, wherein each cable of the plurality ofcables comprises at least one conductor and a shield foil, whereinconductors of the at least one conductor are electrically andmechanically connected to pads of the first plurality of pads. The cableassembly may comprise at least one conductive structure electrically andphysically connected to pads of the second plurality of pads, whereinthe at least one conductive structure comprises a plurality of tabs, andeach tab of the plurality of tabs at least partially wraps around acable of the plurality of cables and is electrically connected to theshield foil of the cable.

The foregoing is a non-limiting summary of the invention, which isdefined by the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings are not intended to be drawn to scale. In thedrawings, each identical or nearly identical component that isillustrated in various figures is represented by a like numeral. Forpurposes of clarity, not every component may be labeled in everydrawing. In the drawings:

FIG. 1A is an isometric view of an electrical cable including a drainwire;

FIG. 1B is an isometric view of a connector configured to operate inconnection with the electrical cable of FIG. 1A;

FIG. 2A is a view of an end of an exemplary drainless electrical cable;

FIG. 2B is a cross sectional view of an exemplary drainless electricalcable;

FIG. 3A is an isometric view of an exemplary conductive structure, inaccordance with some embodiments;

FIG. 3B is a first side view of the exemplary conductive structure ofFIG. 3A;

FIG. 3C is a second side view of the exemplary conductive structure ofFIG. 3A;

FIG. 4A is a plan view of a surface of an exemplary paddle card;

FIG. 4B is a plan view of the opposite side of the exemplary paddle cardof FIG. 4A;

FIG. 5A is a partially exploded view of an exemplary paddle card withconductive structures, in accordance with some embodiments;

FIG. 5B is an isometric view of the exemplary paddle card withconductive structures, of FIG. 5A;

FIG. 5C is an end view of the exemplary paddle card with conductivestructures of FIG. 5A

FIG. 5D is a side view of the exemplary paddle card with conductivestructures of FIG. 5A;

FIG. 5E is a top view of the exemplary paddle card with a conductivestructure of FIG. 5A, with two portions broken out and enlarged;

FIG. 6A is an isometric view of a portion of a cable assembly, inaccordance with some embodiments;

FIG. 6B is an isometric view of the portion of the cable assembly ofFIG. 6A where the cables connect to the paddle card and conductivestructure, in accordance with some embodiments;

FIG. 7 is an isometric view of a cable assembly, partially cut away, inaccordance with some embodiments;

FIG. 8A is an isometric view of an exemplary paddle card with conductivestructures, in accordance with some embodiments;

FIG. 8B is an isometric view of the exemplary paddle card withconductive structures of FIG. 8A, with cables;

FIG. 9A show a first exemplary cable bundle, according to someembodiments;

FIG. 9B shows an exemplary cross-sectional view of a cable of the cablebundle of FIG. 9A, according to some embodiments;

FIG. 10A shows a second exemplary cable bundle, according to someembodiments;

FIG. 10B shows an exemplary cross-sectional view of a cable of the cablebundle of FIG. 10A, according to some embodiments;

FIG. 11 is a performance plot showing far-end crosstalk for a cableassembly, according to some embodiments; and

FIG. 12 is a performance plot showing insertion loss for a cableassembly, according to some embodiments.

DETAILED DESCRIPTION

The inventors have recognized and appreciated structures for providing ahigh frequency, compact cable assembly. The structures may include aconductive structure, such as one or more straps, which includes aplurality of tabs that are configured for electrical contact with anexposed shield of an associated cable of the high frequency compactcable assembly. The conductive structure may be physically mounted to asurface of a printed circuit board (PCB), such that each tab extendsupward from the surface of the PCB. The PCB may be a paddle card of aconnector, and may include multiple pads at least partially disposed onthe surface, such that at least one conductive structure is electricallyand physically connected to some of the pads.

The conductive structure may be electrically connected to a groundstructure within the PCB, providing conductive paths between shields ofthe cables and the ground structure within the PCB. In some embodiments,the conductive structure may have a plurality of portions, each portionconnecting to (a) a ground pad of the ground structure that isassociated with a pair of signal pads of the PCB to which a pair ofsignal conductors are connected, and (b) to the shield of the cableterminated to that pair of signal pads. The portions may be configuredsuch that crosstalk is low where the cables are terminated to the PCB,leading to low crosstalk in the cable assembly. The portion may beintegrally formed from the same conductive material and may have, foreach high speed cable, an attachment to a ground structure of theprinted circuit board. The ground structure of the PCB may include a padon the surface of the PCB near or adjacent the signal pads to which thecable is terminated. Each portion may provide a return path for commonmode signals in a cable. The conductive structure may have openings,exposing the signal pads on the PCB, and facilitating close proximitybetween the signal conducts and an associated return path.

In some embodiments, the tabs of the conductive structure may include afirst set of tabs and a second set of tabs. The first set of tabs may bein a first row, and the second set of tabs may be in a second rowparallel to the first row. In some embodiments, the cable assembly mayinclude a plurality of conductive structures. Each conductive structuremay be electrically and physically connected to ground pads of a subsetof the pads. The plurality of conductive structures may include one ormore U-shaped tabs, one or more single finger tabs at an interiorportion of the conductive structure, or both.

The paddle card of the cable assembly may include signal pads and groundpads on the surface of the PCB. The cable assembly may include aplurality of cables that each includes at least one signal conductor anda shield foil surrounding the signal conductors. The signal conductorsmay be electrically and mechanically connected to signal pads. Theconductive structures may be electrically and mechanically connected tothe ground pads, and each tab may at least partially wrap around a cableto electrically connect to the shield foil of the cable.

The end of the cable may include an exposed portion of the shield foil,which surrounds, at least in part, the at least one conductor. In someembodiments, each cable may include at least two conductors and theshield foil, such as a twinax cable. The cable may have no drain wire.The cables may be electrically and physically mounted to the PCB indifferent rows along the PCB, so that connections for neighboring cablesare staggered along the width of the PCB. One row may include cablesused for transmitting signals, and one row may include cables forreceiving signals. Cables with a plurality of conductors may bephysically and electrically mounted to the PCB, with the conductors fora particular cable mounted side-by-side on the PCB.

A termination structure as described herein may provide low crosstalkbetween signal paths, including low crosstalk between adjacent cableterminations of rows of cable terminations on the paddle card. Such atermination structure may alternatively or additionally provide lowcrosstalk between transmit and receive signal paths, which may beterminated in different rows on the paddle card. In some embodiments,the far end crosstalk may be less than 35 dB over a frequency range of 1to 20 GHz. In some embodiments, the far end crosstalk may be less than40 dB over substantially all of the frequency range, such as more than90% of that frequency range. Such crosstalk may be achieved even forcompact cable assemblies, such as those sufficiently compact to includea paddle card having a width and/or other aspects/dimensions as definedin the OSFP or QSFP-DD standards.

Alternatively or additionally, cable terminations as described hereinmay enable low loss cable assemblies. For example, a cable assembly mayhave cables with a length ranging from 2.5 meters to 3.5 meters, and asignal loss ranging from 15 dB to 20 dB at Nyquist frequency. As aspecific example, a cable assembly may exhibit end to end attenuation ofless than 17 dB at 13.28 GHz with a cable length of 2.5 meters or insome embodiments 3 meters. Such low insertion loss may be achieved witha drainless cable. One or more conductors of each cable can have a gaugeranging between 34 American Wire Gauge (AWG) to 24 AWG, nonetheless, asa result of the cable termination techniques described herein, theseterminations may be sufficiently compact to fit within a paddle cardhaving a width as defined in the OSFP or QSFP-DD standards. Thosetechniques enable closely spaced terminations and use of drainlesscables. As a specific example, an OSFP cable assembly supportingsignaling up to 56 Gbps may have cables with 25 AWG signal conductors, alength of, and a nominal impedance of 100 ohms, with 17 dB or less ofinsertion loss at a 3 meter cable length. As another specific example, aQSFP-DD cable assembly supporting signaling up to 56 Gbps per lane mayhave cables with 27 AWG signal conductors, and a nominal impedance of100 ohms, with 17 dB or less of insertion loss at a 3 meter cablelength.

Cable assemblies as described herein may be configured to supportsignals having any suitable electric bandwidth, such as more than 20GHz, more than 30 GHz or more than 40 GHz. For an illustrative example,PAM4 signaling for Ethernet can achieve 53.12 Gbps. The baud-rate(signaling rate) is 26.56 GBaud. The communicating devices can beintentionally cut-off at 75% of the 26.56 GBaud signaling rate withlow-pass filters (e.g., to ensure a sufficient signal-to-noise ratio).As a result, the effective achievable bandwidth in GHz is 0.75*26.56Gbaud=19.92 GHz. Cable assemblies as described herein may support thatsignaling rate in each of multiple channels.

FIG. 1A illustrates a conventional electrical cable. Electrical cable10, also referred to as “twinax cable”, comprises signal wires 11 and12, which are covered by dielectric coating 13 and 14 respectively. Thesignal wires 11 and 12 may be configured to carry a differential signal,in some embodiments. The cable further comprises a third, uncovered wire15, referred to as “drain wire”. Signal wires 11 and 12 and drain wire15 are surrounded by conductive layer 16, which is configured to serveas an electric shield. The drain wire 15 electrically contacts theconductive layer 16 at multiple locations along the cable (not shown),thus maintaining a ground reference with the conductive layer. Asillustrated in FIG. 1A, the enclosing jacket and the conductive layerhave been removed from the end of the cable to permit termination.

FIG. 1B illustrates a connector 90 configured to terminate one or morecables 10. Connector 90 comprises a circuit board 98 and groundingportion 95. Grounding portion 95 includes a plurality of openings 96,each configured to receive a cable 10. When a cable 10 is inserted intoan opening 96, signal wires 11 and 12 form electrical contacts withcontact portions 93. Furthermore, grounding portion 95 includes aplurality of slots 97, each slot being configured to receive therein thedrain wire of the corresponding cable 10. The grounding portion maycontact the various drain wires, thus keeping the cables grounded andproviding a return path from the paddle card to the wire. While the useof drain wires ensures signal integrity throughout the length of thecable, having to include an additional wire may add weight, may reducethe flexibility of the cable, may take up additional space, and/or thelike.

FIG. 2A is a view of an exemplary cable end 202 of cable 200. The cable200 may comprise a pair of signal conductors 204 and 206. As shown, thesignal conductors 204 and 206 may extend outward at the cable end 202.Any suitable approach may be used to configure the end 202 of the cable200 in this way. A known technique for terminating a cable is to stripaway, at the end of the cable, components of the cable to expose thesignal conductors. In accordance with some embodiments, differentcomponents may be stripped away to expose different components of thecable. For example, the jacket, a conductive layer and dielectric may bestripped away at the distal end of the cable to expose signal conductorsat the distal end of the cable. In other regions, only the jacket may beremoved, exposing the conductive layer.

FIG. 2B is a cross sectional view of the cable 200 at the end 202. Asillustrated, signal conductors 204 and 206 may be surrounded by adielectric material 208, which may be configured to prevent the signalconductors from contacting one another. Alternatively, or additionally,the signal conductors may be coated with a dielectric material. Signalconductors 204 and 206 may be formed from copper or from a copper alloy,such as copper-zinc, copper-nickel, copper-magnesium, copper-iron, etc.Dielectric material 208 may be enclosed within a conductive layer 209,which may comprise a foil, such as aluminized Mylar foil, or wire braidwrapped around the surface of the dielectric material. Conductive layer209 may be configured to provide shielding so as to reduce crosstalkbetween adjacent signal conductor pairs. As illustrated, cable 200 maybe drainless as it does not include drain wires in the illustratedembodiment.

According to one aspect of the present application, the electricalproperties at the termination of the cables (e.g., crosstalk) can beimproved using a conductive member providing ground connections betweencables and a PCB to which those cables are terminated. As discussedfurther herein, the conductive member can provide individual groundpaths for each cable, which can result in improved electrical propertiesat the termination (e.g., compared to connectors without conductivemembers). FIG. 3A is an isometric view of an exemplary conductivestructure 300, in accordance with some embodiments. FIGS. 3B and 3C showa side view and an end view of the exemplary conductive structure 300,in accordance with some embodiments. The conductive structure 300includes a surface 304 that extends along a first direction 306 and asecond direction 308. FIG. 3B shows the side of the conductive structure300 when viewing the conductive structure 300 in the second direction308. FIG. 3C shows an end of the conductive structure 300 when viewingthe conductive structure 300 in the first direction 306.

The conductive structure 300 includes a plurality of tabs 302, each ofwhich extends upwards from the surface 304 of the conductive structure300. In this exemplary embodiment, the tabs 302 extend orthogonal to thesurface 304 and include a bent portion where the tab meets the surface304 of the conductive structure 300.

As discussed in conjunction with FIGS. 5A-5B, the conductive structurecan be designed so that when the conductive structure is mounted to aPCB, the conductive structure is electrically and physically connectedto certain portions of the PCB (e.g., ground pads), while not being inelectrical and/or physical connection with other portions of the PCB(e.g., signal pads). To avoid physical contact with such portions, theconductive structure can include openings that extend in directions 306and 308. In the example shown in FIG. 3A, the conductive structure 300includes a plurality of openings 310 in the surface 304, which aredefined on all sides by the conductive structure 300 such that theconductive structure 300 entirely surrounds the openings 310. However,it is not a requirement that the openings be completely surrounded. Theconductive structure 300 includes a plurality of openings 322 in thesurface 304, which are defined on three sides by the conductivestructure 300, such that the conductive structure 300 partiallysurrounds each of the openings 322, including by projections 324 of theconductive structure 300. While not shown in FIG. 3A, in someembodiments the conductive structure can entirely surround the openings322 (e.g., similar to openings 310).

As shown in this example, one or more of the openings 310 can include aprotrusion 312 that extends downward into a corresponding opening 310.In some embodiments, the protrusions 312 are used to align theconductive structure 300 onto a PCB, such as by fitting into holes inthe PCB. In some embodiments, the protrusions 312 may be soldered to theground structure of the PCB.

In some embodiments, the tabs and openings can be formed and/or disposedin rows of the conductive structure 300. As shown in the exemplaryconductive structure 300, a first set of tabs 302 are in the rowindicated by arrow 314, and second set of tabs 302 are in the rowindicated by arrow 318, with both rows extending along direction 308.The openings 310 are in the row indicated by arrow 316, and the openings322 are in the row indicated by arrow 320, with both rows also extendingalong direction 308. As shown by the arrows 314, 316, 318 and 320, therows are orthogonal to the direction 306. As also shown by the arrows314, 316, 318 and 320, the rows are spaced from each other along thedirection 306.

The conductive structure can be formed from a sheet of metal. Forexample, the conductive structure can be stamped from a sheet and thenportions into the shape shown in FIGS. 3A-3C from a sheet of metal. Theconductive structure 300 includes, for example, a plurality of voids 314from which a subset of the tabs 302 are stamped. The conductivestructure can be made of any type of conductive material, such asstainless steel or other metal.

As discussed herein, the conductive structure can be used in variousapplications, such as for standard-based connectors (e.g., for OSFP,QSFP-DD, etc.). The conductive structure can be mounted (e.g., soldered)to a PCB serving as a paddle card in a plug connector prior toconnection of the cables, so that the conductive structure sits betweenthe cables and the PCB. The conductive structure can be used to provideindividual ground paths to cables, such as cables without drain pads.Some standards specify dimensions of various aspects of the connectors,such as the dimensions of a paddle card, the number, size and locationof solder pads, etc. The conductive structures discussed herein can beused to provide individual ground paths to cables that do not have drainwires, which can reduce crosstalk across cables of the connector. Beingable to omit drain wires from the cables while still providingsufficient electrical characteristics at the terminations can allow thecables to be thinner, to use a thicker (e.g., lower gauge) wire (e.g.,for less loss than thinner wire), and/or both.

FIG. 4A is a plan view of a first side 402 of an exemplary paddle card400, and FIG. 4B is a plan view of the opposite side 404 of theexemplary paddle card 400. The paddle card extends along a firstdirection 450 and a second direction 452. The width of the paddle card4A (here shown as being in the second direction 452) may be specified bythe associated standard, at least at the mating interface where contactpads 406 are located. For example, in some embodiments, the width mayrange between 13.25 and 19.75 millimeters, between 19.5 and 29millimeters, and/or the like. In many commercial implications, thepaddle card will have the same width over its entire length.

Each side 402 and 404 has contact pads 406 and 408 shown in FIGS. 4A-4B.Each side 402 and 404 also has solder pads 410 and 412. The pads can beimplemented in various ways, such as by a layer of metal disposed on thesurface of the paddle card 400 over or otherwise connected to a viawithin the paddle card 400 or as the top of a via within the paddle card400.

The solder pads 410 are arranged along two rows shown by dotted arrows422A and 422B, and the solder pads 412 are similarly arranged along tworows shown by dotted arrows 426A and 426B. Like the contact pads 406 and408 as discussed below, the solder pads 410 and 412 include sets ofsolder pads. There may be a set of solder pads per cable. FIG. 4A showsa first set of solder pads J2, which includes signal solder pads 410Aand 410B and ground solder pad 410C disposed to the right of the signalsolder pads 410A and 410B. In this exemplary embodiment, the solder pads410A, 410B and 410C are used to electrically and physically connect tothe pair of signal wires (denoted “n” and “p” in the figure) and theground of an associated transmit cable (e.g., the first transmit cable),respectively. FIG. 4A also shows a second set of solder pads J4, whichincludes signal solder pads 410D and 410E and ground solder pad 410Fdisposed to the right of the signal solder pads 410A and 410B. In thisexemplary embodiment, the solder pads 410D, 410E and 410F are used toelectrically and physically connect to the n and p signal wires and theground of an associated transmit cable (e.g., the third transmit cable),respectively. The ground solder pads and pairs of signal solder pads ineach row may alternate. For example, the pair of signal solder pads 410Dand 410E are disposed between ground solder pads 410C and 410F, andground solder pad 410C is disposed between signal solder pad pairs410A/410B and 410D/410E.

In some embodiments, paddle card 400 may be constructed such that atleast one of the ground solder pads adjacent a pair of signal pads isattached to a portion of the ground structure within the paddle card towhich the traces attached to the pair of signal pads are referenced. Ifthere is a common mode signal on the pair of traces, for example, therewill be a corresponding return current flow through the ground structureto which those traces are referenced. In a paddle card, for example,ground planes may be interleaved between layers carrying signal tracessuch that the traces are referenced to an adjacent ground plane, whichmay be the closest ground plane to the traces.

The contact pads 406 and 408 are in electrical communication with thesolder pads 410 and 412, respectively, through the interior of thepaddle card. For example, a trace within the paddle card connects solderpad 410A with contact pad 406A; a second trace within the paddle cardconnects solder pad 410B with contact pad 406B; and a ground planewithin the paddle card may connect solder pad 410C with the solder pad410C. As another example, a third trace may connect solder pad 410D withcontact pad 406D; a fourth trace may connect solder pad 410E with thecontact pad 406E. The same, or a different ground plane, may connectsolder pad 410F with solder pad 410F. Thus, like the contact pads 410and 412, the contact pads 406 and 408 can be logically grouped into setsof contact pads associated with the cables terminated to the paddlecard.

For example, each set of contact pads in the contact pads 406 mayinclude a pair of signal pads and a ground pad, which facilitateconnection of the signals from the associated cable to correspondingcontacts of a mating connector. For example, FIG. 4A shows a first setof contact pads, which includes signal contact pads 406A and 406B andground contact pad 406C. In the illustrated embodiment, the groundcontact pads, such as 406C, are longer than the signal contact pads,such as contact pads 406A and 406B. FIG. 4A also shows a second set ofcontact pads, which includes signal contact pads 406D and 406E andground contact pad 406F. FIGS. 4A and 4B show other contact pads thatare not numbered for simplicity. The contact pads 406 are arranged alongtwo rows shown by dotted arrows 420A and 420B, and the contact pads 408are similarly arranged along two rows shown by dotted arrows 424A and424B. Each row includes a plurality of sets of contact pads.

The ground contact pads and pairs of signal contact pads in each row mayalternate. For example, the pair of signal contact pads 406A and 406Bare disposed between ground contact pads 406C and 406F, and groundcontact pad 406F is disposed between signal pairs 406A/406B and406D/406E. As shown, there is a space between the contact pads 406 and408 (e.g., the space between rows 420A and 420B in FIG. 4A). In someconfigurations, pre-wipe pads may be disposed between the rows ofcontact pads 406 and 408 or may be disposed between some or all of thecontact pads in a row proximate an edge of the paddle card and that edge(e.g., as shown in FIGS. 5A-5B).

While not shown in FIGS. 4A-4B, active components can be attached to thepaddle card 400. For example, the paddle card 400 can be sizedsufficiently such that active components can be attached to the paddlecard 400 in the space between the row 420A of contact pads and the row422B of contact pads shown in FIG. 4A. For example, filters, amplifiers,transceivers, and/or the like are examples of active components that canbe attached to the paddle card 400. For example, in some applications itcan be desirable to convert from the communication protocol being usedon the cable to a different communication protocol (e.g., to convertbetween different communication standards). Active components can beincluded on the paddle card 400 to perform the conversion on the paddlecard 400, such that a different protocol is provided to a matingconnector.

In some embodiments, the conductive structures may be electrically andphysically mounted to the solder pads of either or both sides of thepaddle card. In particular, as discussed further herein, the conductivestructures may be sized for electrical and physical connection (e.g.,via soldering) to the ground solder pads of the paddle card. FIG. 5A isa partially exploded view of an exemplary paddle card 500 withconductive structures 502 and 504, in accordance with some embodiments.Paddle card 500 may be constructed like paddle card 400, except with adifferent configuration of contact pads.

As shown in this example, the conductive structure 504 is mounted on thebottom side of the paddle card 500. The conductive structure 502 iselectrically and physically connected to the ground solder pads 506 ofthe top side of the paddle card 500. FIG. 5B is an isometric view of theexemplary paddle card 500, showing the conductive structure 502electrically and physically connected to the paddle card 500. Since theconductive structure 502 is connected to the paddle card 500, the groundsolder pads 506 in FIG. 5A are not visible in FIG. 5B. FIG. 5Bhighlights where the conductive structure 502 is electrically andphysically connected to the ground solder pads 506 using dotted areas508.

FIG. 5C is a first side view of the paddle card, in accordance with someembodiments. FIG. 5C is a view of the end of the paddle card 500, whenviewing the side of the paddle card 500 in the first direction 450 thatis opposite the side at which the conductive structures 502 and 504 areconnected to the paddle card 500. FIG. 5D is a side view of the paddlecard 500, in accordance with some embodiments. FIG. 5D is a view alongthe second direction 452 of the left side of the paddle card. As shown,the tabs 504 extend orthogonal to the surface of the conductivestructure, and include a bent portion 504A where the tab 504 meets thesurface of the conductive structure. As shown in FIGS. 5C and 5D, theconductive structures 502 and 504 are mounted at locations opposite eachother on the respective sides 501A and 501B of the paddle card 500.

In some circumstances, it may be desirable to control the electricalproperties if a cable assembly such as far-end crosstalk. Crosstalk, andother undesirable electrical properties may arise as a result of themanner in which the cables of the assembly are terminated to the paddlecard. A mechanical discontinuity necessarily occurs where the cables,including the signal wires and drain wire (or shield) are connected tothe paddle card. For example, as discussed in conjunction with FIG. 2A,in order to connect cables to the paddle card (e.g., at the solderpads), the layers of the cable (e.g., the conductive layer and thedielectric coatings on the signal wires) are removed so that the signalwire terminations can be connected (e.g., soldered) to the paddle card.Such a discontinuity can give rise to one or more effects that impactthe integrity with which a signal passes through the cable assembly. Forexample, the propagating mode of some of the signal energy carried by acable may change such that not all of the energy in the signal cablewill transition to the paddle card (or vice versa). Some of the energythat does not transition into the paddle card may be radiated, givingrise to crosstalk. Additionally, the mechanical discontinuity can createthe potential for reflections of the signal, which can cause furtherattenuation because the signal energy travels backwards through thesignal wires instead of into the paddle card.

The conductive structure may be configured to provide a cabletermination that has a small impact on signal integrity. The conductivestructure may include portions that create separate ground paths foreach cable (e.g., for each pair of signal wires). The conductivestructure may be shaped and positioned to act as the closest groundconductor to a signal conductor in the cable or connector terminatingthe cable. The conductive structure may be shaped to provide a groundpath for each cable or each signal pair. The conductive structureconnects to the ground portion of the cable (e.g., the shield of acable). Moreover, the conductive structure may be shaped and positionedto provide a spacing between signal conductors and the nearest ground inthe cable termination that smooths any impedance transition between thesignal conductors in the cable and the traces in the paddle card towhich those signal conductors are connected. The conductive structuremay be shaped and positioned to provide an impedance in the signal pathat the termination that approximates the impedance within the signalconductors or within the traces or that transitions between theimpedance in the cable and in the paddle card. Alternatively oradditionally, the conductive structure may be shaped and positionedrelative to the signal path to approximate the spacing between thesignal conductors and the nearest ground in the cable.

Alternatively or additionally, the conductive structures may be shapedand positioned to provide separate ground paths for each signalconductor or pair of signal conductors that approximates the separateground paths for the signal conductors as exists within a cable. Forexample, for a twinax cable with no drain wire, the tabs of theconductive structure mechanically and electrically connect to theexposed shields of the cables of the assembly to complete the conductingpath from the cable shields to the ground structure of the paddle card.That connection may be made to the portion of the ground structure towhich the traces in the paddle card coupled to the signal conductors ofthe same cable are referenced. The separate ground paths may reducecrosstalk because there is less coupling of ground return paths of thecables that are terminated to the paddle card.

FIG. 5E is a top view of the exemplary paddle card 500 with conductivestructure 502 mounted to side 501A, in accordance with some embodiments.Like with FIG. 5B, since the conductive structure 502 is connected tothe paddle card 500, the ground solder pads are not visible in FIG. 5B.FIG. 5E shows where the conductive structure 502 is electrically andphysically connected to the ground solder pads 506 using arrows 554 (thedotted areas 508 used in FIG. 5B are not included in FIG. 5E for clarityand simplicity). The conductive structure 502 includes a plurality ofportions that create separate ground paths for associated signal pads,two of which are shown as portion 550 and portion 570. Each portion iselectrically and physically connected to a ground solder pad that isadjacent an associated pair of signal solder pads. For example, portion550 is electrically and physically connected to ground solder pads atthe portions shown by dotted areas 552A and 552B, and in particular theground pad at area 552A is associated with the signal pads 558 and 560.Portion 570 is electrically and physically connected to ground solderpads at the portions shown by dotted areas 572A and 572B, and inparticular the ground pad at area 572B is associated with the signalpads 578 and 580. Each portion also includes a tab that is aligned withthe pair of signal pads, which, as is discussed in conjunction withFIGS. 6A-6B, is configured to make electrical contact with an exposedshield of a cable terminated to the respective pair of signal pads. Forexample, portion 550 includes tab 556 that is aligned with the pair ofsignal pads 558 and 560. Portion 570 includes tab 576 that is alignedwith the pair of signal pads 578 and 580. Thus, in some embodiments,each portion can associate a return path from the paddle card to thecable that has its signal conductors electrically and physicallyconnected to the pair of signal pads within the portion. As discussedfurther herein, when assembled, the tab aligned with the pair of signalpads folds over the shield of the wire to complete the conducting pathbetween the shield of the cable and the ground structure within thepaddle card via the portion of the conductive structure.

FIG. 6A is an isometric view of a portion of a cable assembly 600, inaccordance with some embodiments. The cable assembly 600 includes aplurality of cables 602 (sixteen cables, in this illustrative example).The cable assembly 600 includes a paddle card 604 with two conductivestructures 606 and 608. FIG. 6B is an isometric view of the portion ofthe cable assembly 600 where the cables 602 connect to the paddle card604 and conductive structure 606. For each cable, the ends of the signalwires are soldered to respective signal solder pads. For example, forcable 602A, the end of the first signal wire 610A is soldered to a firstsignal solder pad, and the end of the second signal wire 610B issoldered to a second signal solder pad. The conductive structure 606also includes a plurality of tabs 614, each of which is folded onto ashield of a respective cable. For example, tab 614A is folded onto theexposed shield of the cable 602A so that the tab is in physical andelectrical contact with the shield. The tabs can be bent around theshields of the cables using, for example, a tool configured tosufficiently bend and press each of the tabs into physical andelectrical contact with the shield without damaging the cable orconductive member (e.g., without crushing the cable). Pressing the tabin a shape to conform to that of the cable, with shield exposed, mayprovide adequate coupling between the conductive member and the shieldof the cable. In other embodiments, an attachment material may be added,including conductive adhesive or solder.

As discussed in conjunction with FIG. 5E, the conductive structureincludes a portion for each cable that provides a ground path for eachcable. For example, the portion 612 of the conductive structure 606creates a ground path for the cable 602A. These ground paths are largelyor wholly disjoint, reducing crosstalk between cables. While not beingbound by any particular theory of operation, the inventors believe thatshaping the conductive structure in this way reduces mode conversion andimpedance discontinuities. Ground paths that are largely or whollydisjoint is also believe to reduce crosstalk between cables. Theconductive structure can be shaped to allow cables to connect to thepaddle cards in different rows (e.g., one row with all transmit signals,and another row with receive signals). Using multiple rows can also helpreduce the effect of crosstalk because cables can be grouped into rowsby signal level (e.g., higher transmit signals can be grouped in onerow, and lower receive signals can be grouped in another row) such thata further separation can be achieved between cables with differentsignal levels (e.g., to avoid crosstalk overwhelming lower signalcables). The ground paths through the conductive structure associatedwith cables in separate rows are completely disjoint, which providesgood electrical separation between conductors most likely to generateharmful crosstalk (e.g. crosstalk from cables with higher signal levelsin one row that could have a substantial impact on lower level signalscarried by conductors in another row).

FIG. 7 is an isometric view of a cable assembly 700, in accordance withsome embodiments. The cable assembly 700 includes outer portions 702 and704 of a plug housing, which are fixed to each other using screws 706.The outer portions 702 and 704 surround the paddle card 708, whichincludes the conductive structures and cable terminations, as discussedin conjunction with FIGS. 6A-6B. The cable assembly 700 includes twocable bundles 710. In region 712 signal wires and other portions of thecables of the cable assembly 700 have been cutaway for illustrativepurposes. The cable assembly 700 also includes a tab 714 connected tolatch release member 716, which can be pulled to release latches of acage into which cable assembly 700 may be inserted to enable removal ofthe cable assembly 700 from the cage. The cable assembly 700 includes astabilization portion 718, which is used to hold the cables relative topaddle card 708 so as to reduce strain on the cable terminations thatmight be caused by forces on the cable. Stabilization portion 718 mayalso provide a housing to facilitate mounting of paddle card 708 in theplug housing. The cable assembly 700 also includes a removable cap 720.

In some embodiments, connector modules may be attached to cables,creating cable assemblies that may be used to connect electronicdevices. Each module may comprise one or more conductive members toterminate one or more cables in the manner described above. The modulesmay comprise mating contact portions configured to mate with matingcontact portions in a mating connector. In the embodiment illustrated,the mating contact portions are rectangular and at the end of the paddlecard. The mating contact portions may include signal and ground pads,and may be configured to mate with mating contact portions in areceptacle.

The plug of cable assembly 700 may mate with a receptacle connectormounted in an electronic device. For example, the receptacle connectormay be mounted on a printed circuit board (PCB) in an electronic device.The cable assembly 700 may be configured to connect any suitableelectronic device to any other suitable device, such as a first computerto a second computer, a computer to a server, and/or the like. The cableassembly 700, including the cables of the cable bundles 710, may havecharacteristics selected for the types of signals to pass between theconnected devices.

FIG. 8A is an isometric view of an exemplary paddle card 800 withconductive structures 802, in accordance with some embodiments. Incontrast to the embodiment of FIG. 5A, for example, in which theconductive structure on each surface of a paddle card was a unitarymember, the conductive structure in the embodiment of FIG. 8A hasconductive structures formed from multiple separate members attached toeach surface of the paddle card.

The first side 806 of the paddle card 800 has four conductive structures802. While not shown, the opposite side (the bottom side opposite side806) also has four conductive structures 802, in the illustratedembodiment. The paddle card 800 includes solder pads 804, which are in afirst row 808 and a second row 810. The first row 808 and second row 810extend along a second direction 814 orthogonal to the first direction812 and are spaced in the first direction 812. The conductive structures802 are electrically and physically connected to the paddle card 800such that two conductive structures 802 are in a third row 816 and twoconductive structures 802 are in a fourth row 818. The third row 816 andfourth row 818 extend along the second direction 814 and are spaced fromeach other along the first direction 812. The conductive structures 802are electrically and physically connected to the paddle card 800 throughrespective ground pads in rows 816 and 818. Alternatively, eachconductive structure 802 may be electrically and physically connected tothe paddle card 800 through a single ground pad. In some embodiments,each conductive structure 802 is electrically and physically connectedto the paddle card 800 through a plurality of ground pads.

Each conductive structure 802 includes tabs disposed along the row towhich the conductive structure 802 is electrically and physicallyconnected. For example, conductive structure 802A includes four tabs820A-D along row 818. Tabs 820A and 820D are each formed at a respectiveend of the conductive structure 802A, and are U-shaped. Tabs 820B and820C include single fingers formed at the interior of the conductivestructure 802A. The tabs of the conductive structures 802 extend upwardsin a direction orthogonal to the surface of the first side 806. The tabsof the conductive structures 802 include a width that extends along thefirst direction 812.

Each conductive structure 802 includes a plurality of portions, such asportion 840 (e.g., two portions). Each portion connects to a ground padof the ground pad structure of the paddle card 800. Each portion isassociated with a pair of signal pads (e.g., signal pads 804A and 804Bfor portion 840) to which a pair of signal conductors are connected.Each portion is connected to the shield of the cable terminated to thatpair of signal pads, including by the finger tab and U-shaped tab of theportion. The portions may be configured such that crosstalk is low wherethe cables are terminated to the PCB, leading to low crosstalk in thecable assembly.

FIG. 8B is an isometric view of the exemplary paddle card 800 withconductive structures 802 and cables 850. As discussed herein, the tabsof the conductive structures are configured for electrical and physicalconnection to the shield of a cable. The conductive structures 802 areshown in FIG. 8B both prior to connection to the conductive shield ofthe cables as well as after connection to the shield of the cables. Forexample, conductive structure 802B is shown prior to connection of itsassociated tabs to the conductive shields of cables 850A and 850B, whileconductive structure 802A is shown with its associated tabs 820A-820D inphysical and electrical contact with the conductive shields of cables850C and 850D. As shown for conductive structure 802A, each pair ofneighboring U-shaped tabs and single finger tabs (e.g., the pair ofU-shaped tab 820A and single finger tab 820B) are configured forconnection to a same cable, such that when the pair of tabs are foldedaround a cable, the single finger tab is disposed within the U-shapedtab.

Each of the conductive structures 802 includes a space portionseparating the tabs of each pair, such as the space 822 between tabs820C and 820D shown in FIG. 8A. The space portions separating the tabsof each pair are sized sufficiently wide enough in the second direction814 to accommodate a cable, as shown in FIG. 8B (e.g., with the cable850D disposed between the tabs 820C and 820D). Each of the conductivestructures 802 also includes a space portion (e.g., the space portion822 of conductive structure 802A in FIG. 8A) disposed between the twopairs of tabs. The space portion between the pairs of tabs is sizedsufficiently wide enough in the second direction 814 to allow a cable topass there between, depending on the row (e.g., rows 816 or 818) inwhich the conductive structure is mounted to the paddle card. Forexample, as shown in FIGS. 8A and 8B, the conductive structures 802 inrow 816 include cables that pass through the conductive structurewithout connecting to the conductive structure, so that the cables canbe mounted to the paddle card in parallel, in a manner such thatneighboring cables connect to solder pads in different rows (e.g., rows808 or 810).

While not shown in FIGS. 6A-8B, in some embodiments a securing membercan be included in the cable assembly to maintain the tabs in electricaland physical communication with the cable shields (e.g., as part of theconnector). The securing member can be sized sufficient to maintain thetabs in electrical and physical communication with the cables withoutdamaging the cables and/or tabs. The securing member can be made of adielectric material, such as a plastic or rubber material.

Various types of cables and/or cable bundles may be used with thetechniques discussed herein. The inventors have discovered techniquesthat enable using a lower gauge wire, which will have less loss in thecables, while still maintaining the same (if not smaller)cross-sectional area when compared to cables with higher gauge signalconductors. For example, for as the frequency of a signal passingthrough a cable is increased, the attenuation of that signal may alsoincrease. Thus, while a lower gauge wire may be larger than a highergauge wire, it can allow for higher frequency applications or longercable assemblies because the lower gauge wire can provide betterattenuation at such frequencies.

The cable assemblies described herein can be designed to achieve cablesof certain lengths that provide certain cable properties (e.g.,impedance, frequency operation, loss, etc.) even when the spaceavailable for terminating the cables is constrained by standards thatlead to paddle cards of limited width. For example, it may be desirableto provide three (3) meter long end-to-end 100 ohm cables with only 17dB of loss via the use of 25 or 27 AWG signal conductors. Theconfiguration of the cables and/or cable bundle can be designed toachieve such cable properties and such cables may be terminated to apaddle card of limited width using techniques as described herein. Insome embodiments, the cables may be constructed without drain wires andthe size and type of dielectric material around the signal conductorsmay be selected to provide cables of a width that may be terminated to apaddle card in accordance with a high density standard. It should beappreciated, however, that the size of the dielectric material cannot bearbitrarily changed to meet mechanical (e.g. size) requirements of astandard because selection of a material size may impact other cableproperties, such as impedance. Nonetheless, the inventors have achieveddesired size and electrical characteristics of cable assemblies usingtechniques as described herein.

FIGS. 9A-9B show a first exemplary cable bundle 900, according to someembodiments. The cable bundle 900 includes eight cables 902, each with arespective pair of signal conductors. For example, cable 902A includessignal conductors 904A and 904B. The signal conductors may be made ofvarious conductive materials. For example, the signal conductors may bemade of copper, silver, gold, a plated copper (e.g., silver platedcopper), a copper alloy (e.g., such as copper-zinc, copper-nickel,copper-magnesium, copper-iron, etc.) and/or the like. The signalconductors may be of various gauges, such as a gauge ranging fromapproximately 34-27 AWG. For example, for a cable assembly that meetsthe QSFP-DD standard, the wires may be 34-27 AWG (e.g., where otherwisethe signal conductors are often 34-25 AWG, or higher).

Each signal conductor is surrounded by a dielectric material. Forexample, the signal conductors 904A and 904B of cable 902A are eachsurrounded by a dielectric material 906A and 906B, respectively. Thedielectric material may be made of any dielectric, such as a polymer(e.g., a foamed fluorinated polymer).

For each cable, the signal conductors and associated dielectrics aresurrounded by a conductive foil. For example, the cable 902A surroundsthe signal conductors 904A, 904B and associated dielectric materials906A, 906B, with conductive foil 908. The conductive foil may be made ofany conductive material, such as aluminum, an aluminum coated polyester(e.g., aluminized Mylar), a wire braid, and/or the like. The conductivefoil may also include an additional layer over the conductive foil, suchas a clear polyester layer.

Various groups of cables and/or layers of cables may be surrounded by abuffer. For example, in the cable bundle 900, two buffers 910A and 910Bare included. The buffer may be made out of a tape, such as polyolefinor polyester tape. Each cable bundle may include one or more outershields. Cable bundle 900 includes an inner shield 912 and an outershield 914. The inner shield 912 may be made of a conductive material,such as aluminum, an aluminum coated polyester, or the like. The outershield 914 may be made of a braided material, such as a copper braid, atinned copper braid, or the like. The wires used in the braid may be ofvarious gauges, such as 36-40 AWG, such as 38 AWG. The outer jacket 916may be a protective material, such as PVC, polyester or the like.

As shown in FIG. 9B for exemplary cable 902A, the signal conductors904A, 904B, dielectric material 906A, 906B, conductive foil 908 andouter coating (e.g., clear polyester, if present), may be configured toachieve certain dimensions for each cable. The first dimension 950 inthe vertical direction may be in the range of 1.25-1.6 millimeters, suchas 1.40 millimeters. The second dimension 952 in the horizontaldirection may be 2.5-2.7 millimeters, such as 2.62 millimeters. Cablesdesigned as shown in FIG. 9A-9B may achieve, for example, an impedanceof 100 ohms and support signals of up to 23 GHz.

FIGS. 10A-10B show a second exemplary cable bundle 1000, according tosome embodiments. The cable bundle 1000 includes eight cables 1002, eachwith a respective pair of signal conductors. Similar to the cables inFIGS. 9A-9B, cable 1002A includes signal conductors 1004A and 1004B,dielectric material 906A and 906B, conductive foil 1008, buffers 1010Aand 1010B, inner shield 1012 and an outer shield 1014, and outer jacket916. The signal conductors in the exemplary able bundle 1000 may be agauge of approximately 25-34 AWG, such as 27 AWG.

As shown in FIG. 10B for exemplary cable 1002A, the signal conductors1004A, 1004B, dielectric material 1006A, 1006B, conductive foil 1008 andouter coating (e.g., clear polyester, if present), may be configured toachieve certain dimensions for each cable. The first dimension 1050 inthe vertical direction may be 1.05-1.25 millimeters, such as 1.17millimeters. The second dimension 1052 in the horizontal direction maybe 2.05-2.25 millimeters, such as 2.16 millimeters. Cables designed asshown in FIG. 10A-10B may achieve, for example, an impedance of 100 ohmsand support signals up to 23 GHz.

The techniques disclosed herein can be used, for example, for data rateapplications specified by the IEEE802.3cd 56 Gbps/lane PAM4 EthernetStandard, which is hereby incorporated by reference herein in itsentirety. An external I/O cable assembly, with a test card usingconductive structures as discussed herein, was built in compliance withthe IEEE802.3cd standard for testing. The test card signal conductorswere 27 AWG, and the test card was compliant with QSFP-DD. The test cardused two ground clips, one on each side of the paddle card.

FIG. 11 is a performance plot 1100 showing the far-end crosstalk (FEXT)for the test assembly, according to some embodiments. The performanceplot 1100 shows FEXT for the eighth receive line (RX8) for side P2 (oneof the end of the cable assembly, where P1 refers to the other end ofthe cable assembly) when each of the first through the seventh transmitlines (TX1 through TX7) are driven. The performance plot 1100 showsplots for TX1 through TX7 at a frequency ranging from 0-26.5 GHz. Asshown in the plot 1100, the FEXT of the transmit lines is substantiallyless than 40 dB over a frequency range of 0-26.5 GHz (e.g., for over 90%of the frequency range), with crosstalk for most of the transmit linesbeing less than 40 dB over the range. The worst case crosstalk, for TX1,exceeds 40 dB by only a few dB (e.g. less than 2) for a small subrangeof the frequencies.

FIG. 12 is a performance plot 1200 showing the differential insertionloss (SDD21), or insertion loss (IL), for the test assembly, accordingto some embodiments. The performance plot 1200 shows IL for lines 1-8when transmitting from both side P1 to side P2 as well as from side P2to P1. For example, P1TX1-P2RX1 shows the differential insertion lossfrom side P1 on TX1 to the RX end of line TX1 at side P2 (P2RX1). Asanother example, P2TX1-P1RX1 represents a transmission from side P2 onTX1 to side P1, which is the RX end of line TX1 (P1RX1)). Theperformance plot 1200 shows traces for each transmission at a frequencyrange from 0-27 GHz. The performance plot 1200 also shows the 802.3cdMax IL. As shown in plot 1200, for both transmit and receive signaling,the IL increases as the frequency increases, starting at around 0 andincreasing to an IL ranging between approximately 27-36 dB, with oneline showing an IL that exceeds that by a small amount (e.g. a few dB)around 25 GHz.

Crosstalk and IL as shown in FIGS. 11-12 reveal a cable assembly wellsuited for use for high frequency signals, including those in the rangeof 0-27 GHz, in an assembly with multiple lanes, such as those that meetthe OSFP or QSFP-DD standards. Such cable assemblies may, for example,meet the QSFP-DD standard with 27 AWG signal conductors that are 2.5meters with end to end attenuation of less than 17 dB. As anotherexample, a cable assembly may meet the OSFP standard with 25 AWG signalconductors that are 3.0 meters with end to end attenuation of less than17 dB.

Having thus described several aspects of at least one embodiment of thisinvention, it is to be appreciated that various alterations,modifications, and improvements will readily occur to those skilled inthe art.

For example, embodiments are described that meet the requirements ofOSFP and QSFP-DD standards. Techniques as described herein may beapplied to cable assemblies that meet other standards or are customconfigurations that are not designed for specific standards.

Similarly, embodiments are described for use with double densityconfigurations in which contact pads on a paddle card are arrayed in tworows. The same techniques may be used in other configurations, includingwith paddle cards with a single row or more than two rows of contactpads and/or solder pads.

As another example, a round cable bundle is illustrated. Techniques asdescribed herein may be used with ribbon cables or cable bundles inother configurations. Likewise, cables are described as having twosignal conductors that are wrapped with a shield. Other cableconfigurations may be used, such as ribbon cables in which two shieldingfilms are pinched on either side of each of multiple sets of signalconductors.

Such alterations, modifications, and improvements are intended to bepart of this disclosure, and are intended to be within the spirit andscope of the invention. Further, though advantages of the presentinvention are indicated, it should be appreciated that not everyembodiment of the invention will include every described advantage. Someembodiments may not implement any features described as advantageousherein and in some instances. Accordingly, the foregoing description anddrawings are by way of example only.

Various aspects of the present invention may be used alone, incombination, or in a variety of arrangements not specifically discussedin the embodiments described in the foregoing and is therefore notlimited in its application to the details and arrangement of componentsset forth in the foregoing description or illustrated in the drawings.For example, aspects described in one embodiment may be combined in anymanner with aspects described in other embodiments.

Also, the invention may be embodied as a method, of which an example hasbeen provided. The acts performed as part of the method may be orderedin any suitable way. Accordingly, embodiments may be constructed inwhich acts are performed in an order different than illustrated, whichmay include performing some acts simultaneously, even though shown assequential acts in illustrative embodiments.

Also, circuits and modules depicted and described may be reordered inany order, and signals may be provided to enable reordering accordingly.

Computer-executable instructions may be in many forms, such as programmodules, executed by one or more computers or other devices. Generally,program modules include routines, programs, objects, components, datastructures, etc. that perform particular tasks or implement particularabstract data types. Typically, the functionality of the program modulesmay be combined or distributed as desired in various embodiments.

Also, data structures may be stored in non-transitory computer-readablestorage media in any suitable form. For simplicity of illustration, datastructures may be shown to have fields that are related through locationin the data structure. Such relationships may likewise be achieved byassigning storage for the fields with locations in a non-transitorycomputer-readable medium that convey relationship between the fields.However, any suitable mechanism may be used to establish relationshipsamong information in fields of a data structure, including through theuse of pointers, tags or other mechanisms that establish relationshipsamong data elements.

Use of ordinal terms such as “first,” “second,” “third,” etc., in theclaims to modify a claim element does not by itself connote anypriority, precedence, or order of one claim element over another or thetemporal order in which acts of a method are performed, but are usedmerely as labels to distinguish one claim element having a certain namefrom another element having a same name (but for use of the ordinalterm) to distinguish the claim elements.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified.

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e., “one or more” ofthe elements so conjoined. Other elements may optionally be presentother than the elements specifically identified by the “and/or” clause,whether related or unrelated to those elements specifically identified.Thus, as a non-limiting example, a reference to “A and/or B”, when usedin conjunction with open-ended language such as “comprising” can refer,in one embodiment, to A only (optionally including elements other thanB); in another embodiment, to B only (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of.” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

Also, the phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” or “having,” “containing,” “involving,” andvariations thereof herein, is meant to encompass the items listedthereafter and equivalents thereof as well as additional items.

What is claimed is:
 1. A cable assembly comprising: a paddle cardcomprising a planar surface, wherein the paddle card comprises a firstplurality of pads and a second plurality of pads on the planar surface;a plurality of cables, wherein each cable of the plurality of cablescomprises at least one conductor and a shield foil, wherein conductorsof the at least one conductor are electrically and mechanicallyconnected to pads of the first plurality of pads; at least oneconductive structure electrically and physically connected to pads ofthe second plurality of pads, wherein: the at least one conductivestructure comprises a second surface adjacent to and parallel to theplanar surface of the paddle card and a plurality of tabs extending fromthe second surface; and each tab of the plurality of tabs at leastpartially wraps around a respective cable of the plurality of cables andis electrically connected to the shield foil of the respective cable. 2.The cable assembly of claim 1, wherein: the first and second pluralityof pads comprises pairs of neighboring signal pads and ground padsdisposed between adjacent pairs of signal pads; each cable of theplurality of cables comprises two conductors, wherein the two conductorsof each cable are mounted to a respective pair of neighboring signalpads; the at least one conductive structure comprises a plurality ofportions, each portion: being electrically and physically connected to aground pad of the set of pads adjacent a respective pair of signal padsof the set; and comprising a tab of the plurality of tabs aligned withthe respective pair of signal pads so as to make electrical contact withan exposed shield of a cable terminated to the respective pair of signalpads.
 3. The cable assembly of claim 1, wherein: an end of the cablecomprises an exposed portion of the shield foil; and the shieldsurrounds, at least in part, the at least one conductor.
 4. The cableassembly of claim 1, wherein each cable of the plurality of cables is atwinax cable without a drain wire.
 5. The cable assembly of claim 1,wherein: the paddle card comprises a length that extends along a firstdirection; the first and second plurality of pads are disposed in afirst row and a second row, wherein the first row and the second rowextend along a second direction orthogonal to the first direction, andthe first row is spaced from the second row in the first direction; thecables of the plurality of cables are aligned in parallel in the firstdirection and disposed side-by-side in the second direction; and theplurality of cables are electrically and physically connected in analternating fashion such that conductors of neighboring cables of theplurality of cables are electrically and mechanically connected to padsof the first plurality of pads in different rows of the first and secondrows.
 6. The cable assembly of claim 5, wherein: cables of the pluralityof cables with conductors electrically and mechanically connected topads of the first plurality of pads in the first row are configured topass signals in a first direction; and cables of the plurality of cableswith conductors electrically and mechanically connected to pads of thefirst plurality of pads in the second row are configured to pass signalsin a second direction different than the first direction.
 7. The cableassembly of claim 1, wherein: the paddle card comprises a length thatextends along a first direction; the paddle card comprises a width thatextends along a second direction orthogonal to the first direction,wherein the width is between 13.25 and 19.75 millimeters.
 8. The cableassembly of claim 7, wherein: the plurality of cables comprises eighttwinax cables; and the at least one conductor of each cable of theplurality of cables comprises a gauge ranging between 34 American WireGauge (AWG) to 25 AWG.
 9. The cable assembly of claim 1, wherein: thepaddle card comprises a length that extends along a first direction; thepaddle card comprises a width that extends along a second directionorthogonal to the first direction, wherein the width is between 22 and27 millimeters.
 10. The cable assembly of claim 9, wherein: theplurality of cables comprises eight twinax cables; and the at least oneconductor of each cable of the plurality of cables comprises a gaugeranging between 34 American Wire Gauge (AWG) to 25 AWG.
 11. The cableassembly of claim 1, wherein the electrical connection of the pluralityof tabs of the at least one conductive structure to the shield foil ofeach cable suppresses crosstalk between the cables of the plurality ofcables.
 12. The cable assembly of claim 11, wherein a far end crosstalkof the plurality of cables is less than 35 dB over a frequency range of1 to 20 GHz.
 13. The cable assembly of claim 11, wherein a far endcrosstalk of the plurality of cables is less than 40 dB substantiallyover a frequency range of 1 to 20 GHz.
 14. The cable assembly of claim1, wherein the plurality of cables comprise: a length ranging from 2.5meters to 3.5 meters; an impedance of 100 ohms; and end to endattenuation of less than 17 db.
 15. The cable assembly of claim 1,wherein the at least one conductive structure comprises a plurality ofcontiguous openings, wherein each contiguous opening of the plurality:extends along the planar surface in a first direction and a seconddirection; and surrounds at least one pad from second plurality of pads,such that the at least one conductive structure is not in mechanicalcontact with the second plurality of pads.
 16. The cable assembly ofclaim 1, wherein: the paddle card comprises a ground structure withinthe paddle card; and the at least one conductive structure iselectrically connected to the ground structure via the second pluralityof pads.
 17. A cable assembly comprising: a paddle card comprising afirst edge, a plurality of mating contacts adjacent the first edge, asurface, a plurality of pads on the surface, and a ground structurewithin the paddle card; a plurality of cables, wherein each cable of theplurality of cables comprises at least one conductor and a shield foil;at least one conductive structure electrically coupled to the groundstructure within the paddle card and electrically and mechanicallycoupled to the shield foil of a respective cable, the at least oneconductive structure comprising a second surface adjacent to andparallel to the surface of the paddle card, wherein: the mating contactsare elongated in a first direction orthogonal to the first edge; theplurality of pads are disposed in a first row and a second row; thefirst row and the second row extend along a second direction orthogonalto the first direction, and the first row is spaced from the second rowin the first direction; the first and second rows are in a regionbetween the first edge and a second edge opposite the first edge; andthe first and second rows comprise sets of pads that each comprise apair of signal pads of the plurality of pads; and the plurality ofcables comprises a first subset and a second subset, with the at leastone conductor of the cables in the first subset electrically andmechanically connected to pads of the plurality of pads in the first rowand the at least one conductor of the cables in the second subsetelectrically and mechanically connected to pads of the plurality of padsin the second row.
 18. The cable assembly of claim 17, wherein: themating contacts comprise signal contact pads, wherein each signalcontact pad is in electrical communication with an associated signal padof the plurality of pads; and ground contact pads, wherein each groundcontact pad is in electrical communication with an associated ground padof the plurality of pads.
 19. The cable assembly of claim 17, whereinthe sets of pads of the first and second rows each further comprise aground pad of the plurality of pads adjacent the pair of signal pads.20. The cable assembly of claim 19, wherein the at least one conductivestructure is electrically connected to the ground structure via theground pads of the first and second rows.
 21. The cable assembly ofclaim 17, wherein the at least one conductive structure comprises aplurality of openings, wherein each opening of the plurality: extendsalong the surface in the first direction and the second direction; andis shaped to surround a pair of signal pads in the first row or thesecond row on at least three sides.
 22. A cable assembly comprising: apaddle card comprising a surface, wherein the paddle card comprises aground structure within the paddle card, a plurality of pads on thesurface, and a plurality of openings in the surface; a plurality ofcables, wherein each cable of the plurality of cables comprises at leastone conductor and a shield foil, wherein conductors of the at least oneconductor are electrically and mechanically connected to pads of theplurality of pads; at least one conductive structure comprising a secondsurface adjacent to and parallel to the surface of the paddle card and aplurality of tabs extending from the second surface, wherein: each tabof the plurality of tabs at least partially wraps around a respectivecable of the plurality of cables and is electrically connected to theshield foil of the respective cable; and the at least one conductivestructure comprises a plurality of protrusions that extend intocorresponding openings of the plurality of openings, whereby theconductive structure is electrically connected to the ground structurewithin the paddle card.